One of the most popular types of heaters currently available, a radiant heater can be found in nearly every home in North America. Whether it’s a small space heater, or part of a larger radiant heating system, radiant heaters serve a large portion of the population’s heating needs. One of the oldest heating systems around, the best example of radiant heat is the warmth from sunshine.
Radiant heat is the transfer of energy from an emitting heat source to an object. This basic principle can be achieved through several methods, but one of the oldest and most widely practiced forms of radiant heating is having a fire in a fireplace. A fireplace emits radiant heat, and draws in cold air from the room, which forms a heating cycle. Air needed for combustion is drawn in from other parts of the room and outdoors, while hot exhaust leaves the building though the chimney, where it heats the rest of the building though convection heating. The people and objects in the room absorb the radiant heat from the high temperature flames, because solid objects are the first things to feel radiant heat. Eventually, the overall air temperature will catch up, but that may take some time.
For a while, radiant heating was the only form of heat people had access to, because convection heating systems hadn’t been developed yet; but we’ve come to a point where convection heating and radiant heating have become technological equals. If anything, radiant heating systems had to play catch-up. For a very long time, steam radiators were the most popular form of radiant heater, but new developments have made steam radiators seem decidedly outdated.
Radiant heating can be used both indoors and outdoors. Some of the most common outdoor radiant heating systems are used to melt snow and de-ice roofs. Also many outdoor patio heaters use the same radiant heating principle.
Some of the most popular models of radiant heaters (wiki) come in the form of a simple infrared space heater. There are many different models of infrared space heater (wiki), but they all work on the same principle. The heater is usually comprised of some form of metal filament inside of a heat-resistant quartz envelope. The heater then runs an electrical current through the quartz elements, and then the quartz being used to emit infrared light and heat. Infrared heaters are over 86 percent fuel efficient, with the rest being lost to convection heating. The device literally radiates heat in the same way the sun radiates heat. One of the best ways to describe an infrared heater is that it heats objects more than air. The infrared heat passes though the air and makes direct contact with people and objects making them feel warm before the air temperature rises. Another good way to describe the feeling of a radiant space heater is that it feels like sitting in front of a roaring fire.
The heater’s BTU output is directly related to the amount of quartz filaments in the device and the size of the heater. Large devices with elongated filaments distribute heat much more efficiently than smaller models. Some models of infrared heater can be used to heat an entire room, while others only radiate heat for a few feet before dissipating.
There are quite a few things to look for in an infrared heater including:
- Wattage – The device’s heat output is directly related to wattage, so keep that in mind when purchasing a space heater. Infrared heaters use the wattage much more efficiently than other types of space heater, so a 750-watt infrared heater will be more powerful than a 750-watt convection heater
- Safety – Another important thing to keep in mind when buying any heating device is whether or not the device is safe to use. Many accredited companies test and certify space heaters, so there’s almost no excuse for a device without some form of safety certification. For instance, the UL, Underwriters Laboratory, tests heating devices, and a UL sticker can be found on many heating devices. It is not advised to use a device that doesn’t have full safety certification
- Capacity – One of the most important aspects of any heater is the device’s capacity. The heater’s capacity refers to the device’s ability to heat a certain area, usually measured in square feet. For instance, the average 1500-watt infrared space heater has a capacity of about 300 or 400 square feet, depending on the size of the heater and the amount of quartz heating elements
- Extras – The majority of infrared heaters come with many useful features, but some of the most useful functions a heater can provide come as extras. One of the most common extras to find on a infrared heater is a programmable thermostat or timer. Both of these functions make using the device much easier, but they’re not required for the device to work properly.
Home Radiant Heating Sources
Every heating system has three parts: the heat source, the heat distribution system, and the control system. While many heaters break these three parts into three different devices, some systems prefer to have the all combined into one device.
Hot water boilers can connect to many types of heating systems, but they were primarily connected to steam radiant systems for the better part of the last century. Most modern boilers go to a hot-water baseboard, but that system uses more convection heat than radiant heat. A boiler is a rather sophisticated machine that heats water to provide hot water or steam to every part of the home. The heated water is almost always distributed around the house through a series of pipes, which can connect to either to a radiant heating system or a steam radiator. A boiler is about 50 percent to 90 percent efficient depending on how old it is and what fuel it’s using. Boilers can use almost any type of fuel including: natural gas, propane, heating oil, bio-diesel, or electricity. The average boiler is expected to last about fifteen to thirty years before it needs to be replaced. Maintenance on a boiler is minimal, and you don’t have to worry about cleaning and replacing vents.
Popular devices among modern homeowners, heat pumps pull heat from the surrounding air to warm the house. The same process can be used for cooling, but that doesn’t have much to do with radiant heating. A heat pump has a life expectancy of about fifteen years and doesn’t require very much maintenance. The device can run off geothermal energy or electricity, which makes it very fuel efficient and cheap to run (info). Heat pumps can connect to a number of heating systems, but they are primarily used in radiant floor heating systems.
Home Radiant Heating Distribution
Also called under-floor heating, radiant heating is a form of central heating, which changes the indoor clime and provides thermal comfort through radiant heat rising through the floor. Under floor heating has been used for many years, but recent developments have added a great deal to the original under-floor heating design. Radiant heating uses electrical resistance elements or fluid flowing in pipes to heat the floor and the room above. While the systems are usually installed in the floor, many people have begun installing them in walls and ceiling to increase heat distribution. One of the reasons people like radiant heating so much is because it doesn’t spread dust, dirt, and allergens through the house in vents. Instead, the device has the heat rise from the floor to heat the room above without forcing or blowing any air. One of the only problems with this form of radiant heating is that it can cost quite a bit to have the system installed, and maintenance can be difficult.
One of the first modern forms of radiant heating, a steam radiator uses steam flowing through pipes while under pressure to radiate heat into a room. As the steam passes though a series of coiled pipes it diffuses heat into the room. There were several issues with using steam radiators, so the majority of them were removed from homes and replaced with other systems. If condensation formed in the horizontal sections of the steam pipe, the radiator would produce a banging sound called a water hammer. This effect can be avoided by bleeding the heater of all the trapped air and water vapor that is impeding the path of the steam.
Hot Water Radiant Heater
A hot-water radiator is made up of a sealed, hollow, metal tube filled with water by a gravity feed, pressure pump, or through convection. As the water-filled pipes give off heat the hot water cools and sinks to the bottom of the radiator or is forced out the other end of the pipe and back into the heating system.
Hot water, baseboard radiators have become much more popular with the decline of traditional cast iron radiators. A modern baseboard heater consists of two copper pipes covered in aluminum fins inside of a protective metal chassis. The aluminum fins on the pipes increase the overall surface area and help transfer more heat to the room.
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